The present disclosure relates to photovoltaic device manufacturing, and more particularly, to methods for controlling the removal of a surface layer from a substrate utilizing spalling.
A photovoltaic device is a device that converts the energy of incident photons to electromotive force (e.m.f.). Typical photovoltaic devices include solar cells, which are configured to convert the energy in the electromagnetic radiation from the Sun to electrical energy. Multi junction solar cells comprising compound semiconductors may be employed for power generation in space due to their high efficiency and radiation stability. Multi junction solar cells are mainly fabricated on germanium (Ge) substrates due to the inherently strong (IR) absorption property of germanium (Ge). Germanium (Ge) also includes a crystal structure that can be lattice matched to III-V compound semiconductors, which allows for integration of III-V sub cells on a germanium (Ge) substrate. The germanium (Ge) substrate may constitute nearly 50% to 70% of the final cost of the finished solar cell.
There is a trend within the photovoltaic industry to continually minimize the amount of semiconductor material used to fabricate solar cells, while maximizing energy conversion efficiency. The high-cost associated with producing semiconductor materials degrades the cost per Watt metric of a given photovoltaic technology. Also, expensive semiconductor material that is not contributing to energy conversion can be considered waste at the device level.